Method of making electric contact devices



Get. 14, 1947. A. M. COHENY 2,429,048

METHOD OF MAKING ELECTRIC CONTACT DEVICES Original Filed June 28, 1942 MAW/1.9 770)! 7 1 7 Patented Oct. 14, 1947 METHOD OF MAKING ELECTRIC CONTACT DEVICES Arthur Cohen, N w Rochelle, N. assignoi to Ward Leonard Electric Company, a corporat tion of New York Original application June 25 19 i2, SerialNo.

448,352, now Patent No. 2,340,579, dated Febr'uary 1, 1944.

Divided and this application March 26, 1943, Serial No. 480,629

4 Claims". 1

This invention relates to the method of making a, multiple contact device wherein a movable contact element variably engages a number of fixed contacts for the control of circuit connections and is applicable particularly to rheostats for changing the connections of the resistive conductors.

This application is a division of my original pending application Serial Number 448,352, filed June 25, 1942, Patent No. 2,340,579, and covers the improved method of making the structure, my original application covering the improved strucure In the United States patent of Frank G. Logan granted December 19, 1941, No. 2,266,222, an improved rheostat and contact structure for varying the resistance is disclosed and in which a straight row of contacts is controlled by a movable contact bar of wide open V form with an obtuse angle between two arms of the movable contact; The patent also discloses a form where a straight movable contact bar is utilized and wherein the row of contacts engaged thereby forms a wide open V with an obtuse angle between the two arms of the row of contacts. This latter relationship of contacts has particular advantages in certain uses but the making of a row of contacts in the form of a Wide open V introduces difiiculties in the cost of manufacture, the support and union of the two arms and the securing of sufficient strength and rigidity of the parts and accuracy of workmanship.

One of the main objects of the present invention is to provide a new and simplified method of making and assembling the row of contacts in V form and in providing a structure which may be readily and conveniently made. Another object is to rovide a structure which may be made with a high degree of accuracy and be rigid and of a compact form and durable and dependable under long continued use. Another object is to provide a structure in which comparatively small movement of the movable element will secure a pronounced change of the contacts engaged thereby, giving pronounced control with comparatively small relative movement of the parts. Another object is to permit the use of a straight movable contact bar of light weight with resulting low inertia and with low friction of the parts. These objects and advantages of this improvement render it particularly advantageous for use in regulators wherein it is desired that the movable contact element be responsive to slight changes of the controlling influence and wherein a pronounced change is desired under comparatively small variations of control factor. The improved structure is particularly well adapted for control by an electromagnet in which the current, or change of current, in the winding of the magnet imposes the desired control and corrective effect. Other objects and advantages will be understood from the following description and accompanyi'n'g drawings illustrating one embodiment of the invention.

1 is a plan view of the fixed element, the movable element not being shown for clearness; Fig. 2 is a rear elevation showing the movable contact element in position; Fig. 3 is a plan view with the movable element in position; the showing of the individual fixed contacts and intervening insulation being omitted for the purpose of more clearly showing the different planes of the fixed contact device; Fig. 4 is an end view of the apparatus; Fig. 5 is a sectional view on the line 55 of Fig. 1 and also showing the movable contact; Fig. 6 is a sectional View on the line 6--6 of Fig, 1 also showing the movable contact; and Fig, 7 is a face view of one of the fixed contacts in its original form before assembly and completion of the structure.

The fiXed contact elements could be assembled so that the two rows of contacts form an obtuse angle with each other by mounting the contacts on two straight arms and then joining the two arms together at the apex; but this requires a considerable amount of handwork and involves difiiculty of properly joining and supporting the parts and unless particular care is exercised, results in lack of uniformity and accuracy in the relationship of the parts. Another method is to utilize a straight central support and assemble the fixed contacts and intervening insulation on the support and maunally adjust the individual contacts of proper form on the support so as to bring the contacting edge or surface of each contact in a line to form a wide open V or obtuse angle between the arms; but this greatly increases the handwork and time of assembly and if the contacting surfaces or edges of the fixed unit are to be positioned in the same plane which is the most desirable and practical arrangement, it requires that each of the fixed contacts in the two arms of the V must be different in shape from each of the others. Such a, method results in lack of uniformity and inaccuracies in the final product. By the present invention these difiiculties are overcome.

In this improvement each of the fixed contact elements are of the same form originally and are assembled on a straight supporting element with provision of proper insulation and then the parts are ground or machined to secure the desired wide open V form of contact surfaces and by reason of the fact that the contact surfaces of the fixed element are in the same plane, it permits the use of a straight movable contact bar movable in one plane for engagement therewith. There is the further advantage of enabling the use of a movable straight bar contact in the form of a roller which avoids the friction of a sh ing contact engagement. This reduction in friction is particularly advantageous where sensitiveness of response is required in regulators and other controlling apparatus.

Referring to Fig. l, the contacts are supported by a straight metal rod l which extends through a series of fixed contacts. This rod is threaded at each end and the nuts 2 and washers 3 engage opposite ends of the rod for securely clamping the parts together. In the form shown, a block Q of insulating material engages the central portion of the rod for supporting the fixed contact device and is shown of square cross section with a screw do at its outer end for clamping the device to any suitable support 4b. Instead of supporting the fixed contact device by this central support, it could, if desired, be supported at the ends of the rod Adjoining the metal washers 3 at each end of the device is an insulating washer and between each of these and the central support is a tube 6 of insulating material as shown in Figs. 5 and 6 which is mounted on the supporting rod l. These tubes serve to insulate the fixed contacts from the supporting rod.

The original form of each of the fixed contacts 7 is shown in Fig. 7 and is in the shape of a round disk having a central opening la for permitting them to be slipped over the insulating tube 6. Each contact is provided with an extension lb at one side, the outer end of which is perforated for convenient connection thereto of the lead wires which are connected to resistive controlling elements in proper order or to other devices for securing the desired controlling effect according to the particular use to be made of the apparatus.

At each side of the central support 4 is mounted a series of plain circular disks 8 of the same form as shown in Fig. 7 without any extension lb; and adjoining each of the washers 5 is a series of rings 9 similar to the rings 8. The rings 8 and 9 have no insulation between them and serve to form the inner and outer terminals for engagement by the movable contact bar. Instead of building up these terminal contacts 8 and 9 of a series of rings, they could be formed of a single wide ring. The contacts I and the rings 8 and 9 are preferably made of good conducting material and in order to insure good contact with the movable contact element are preferably made of coin silver or a silver alloy.

The contacts I are mounted on the insulating tubes 3 between the contacts 8 and 9 respectively with an intervening washer H] of insulating matcrial separating each of the contacts from each other. In assembling the rings 1, their extensions lb are positioned in staggered relation to each other as indicated in Figs. 1 to 3 and as well shown in Figs. 4 to 6. After the parts are assembled as described, the nuts 2 are tightened for securely clamping the assembled parts toether. The staggered extensions from the contact rings are positioned below say the lower half of the assembled unit which leaves the upper half of the tubular assembly of cylindrical form. This arrangement is for exposing the upper portion of the unit to the machine or grinding operation by which the wide open V form of contact surfaces is provided.

The first operation in shaping the contacts is to grind a flat surface on the top of the assembled contacts. The depth of this grinding operation is of a sufficient amount to insure that each of the contact elements will have a surface positioned in the same plane as each of the other contacts on a line of wide open V form adapted to be engaged by the movable contact bar. The next operation is to form an inclined surface or plane generally indicated at 12 at one side of the central portion of the assembled elements. This plane is at an angle to and below the horizontal plane through the previously ground fiat surface and is likewise at an angle to a vertical plane which plane is at right-angles to the axis of the assembled elements. The inclination of the plane 12 is well shown in Figs. 5 and 6. The plane I2 is formed by milling or preferably by surface grinding and owing to its inclination forms a line In in the previously ground fiat surface which gives the inclination of one leg of the V contact engaging surfaces. The next surface to be formed may be considered as the surface I3 at the left of Fig. l and on the opposite side of the line I'm from the surface 12. The surface i3 is similarly inclined to a horizontal plane and to a vertical plane which latter is at right-angles to the axis of the assembled elements and extends in a downward direction from the horizontal plane. The inclination of the plane i3 is well shown in Figs. 5 and 6. This surface may be formed by milling or by surface grinding and extends to a line [3a which is quite close to the line l2a and thereby forms a flat narrow contact surface of one leg of the V.

Similarly the surface I4 at the right of the support 4 is ground down in a plane which extends below and at an angle to the horizontal surface and likewise at an angle to a vertical plane, the angle to the vertical plane being indicated by the line Ma to which the surface M i ground. The line Ma lies in the plane of the previously ground fiat top surface. The inclination of the plane I4 is shown in Fig. 4. Likewise the surface 15 is ground down on the opposite side of the line Ma at an angle to vertical and horizontal planes, the inclination being shown in Fig. 4. The milling or grinding of this surface i5 is such that it extends to a line l5a quite close and parallel to the line Ma, thereby forming a flat narrow contact surface which is the other leg of the wide open V form of contacts. The edges of the rows l2a, l3a, Ida and l5a of the two contact legs may be polished and rounded slightly by hand and buffed.

he method of making the fixed unit as above described permits the parts to be readily and quickly assembled and the surface grinding for forming the inclined planes and the rows of contact surfaces in the Wide open V relationship may be quickly and accurately accomplished. The result is a rigid, compact, permanent structure wherein the contacting surfaces are quite accurately formed and aligned. This structure and method of making also permits the use of thin contact rings, giving a considerable change of the contacting surfaces with comparatively small movement of the movable element. The angle of divergence of the inclined surfaces from the line of contacting surfaces may be comparatively small so that a relative small amount of material is ground away. Also this small angle of divergence requires less handwork in the polishing of the edges of the contact surfaces than would otherwise be required, or no handwork at all may be necessary.

The movable contact may be a straight bar of conducting material actuated by the controlling influence and engages and moves over the two legs of the row of contacts; and by its variable movement will short-circuit more or less of the elements connected to the contact rings or secure other controlling effects according to the connections of the contact rings. The bar is preferably in the form of a straight roller [6 mounted on a supporting rod 16a and rotatably supported in the ends of a bail I! actuated and controlled by its support Ila. This support is controllable by an electromagnet or other responsive device for variably adjusting the roller to give the desired control. Instead of providing a central supporting rod for the roller, it may be made a solid bar with reduced end portions for engagement with the bail IT. The roller is preferably made of an alloy of silver for insuring good electrical contact with the contacting surfaces of the fixed contacts. It is evident that when the roller is in the position shown in Fig. 3, it bridges the end contacts 9 and thereby shortcircuit all of the devices connected to the various contact rings; and when the roller is advanced to its other extreme position it will engage only the contacts 8, thereby permitting all of the devices connected to the respective contact rings to be effective in the controlled circuit or circuits. But when the roller is in an intermediate position, it will afiect the controlled circuit or circuits according to its adjustment in a manner well understood by those skilled in the art.

Instead of making the two rows of contacts of wide open V form, they could be arc-shaped or of bow form, or be in a curved plane, or be of any other equivalent form to secure approximately the same results without departing from the scope of the appended claims. Also the inclined surfaces which diverge from the rows of contact surfaces instead of being flat surfaces may be somewhat curved, such as of concave or convex conical form, or made up of a series of flat surfaces combined to diverge in a general direction from the rows of contacts. Furthermore these surfaces need not necessarily be inclined or diverged from the contact rows, it being basically sufficient to cut away material from the body of the unit to form the projecting rows of contact surfaces at an angle to each other, such as by forming surfaces all in the same plane, or nearly so, below the plane of the rows of contacts.

Although a preferred embodiment of the invention has been described and a preferred method of making, it will be understood that various modifications may be made without departing from the scope of the invention.

I claim:

1. The method of making an electric contact device which comprises assembling on a central axially extending insulating support a series of conducting elements of the same shape as each other with intervening insulating washers between each of the elements, clamping said ele ments and washers together to form a unit, and removing a portion of the material at one side of a central plane perpendicular to the axis to form an edge at an angle to the central axis, removing another portion of the material from the same side of said central plane and from the opposite side of said edge to form a leg of projecting contact surfaces at an angle to the central axis, and similarly removing two portions of material from the opposite side of said central plane and thereby forming another leg of projecting contact surfaces converging with said first-named leg toward a central apex.

2. The method of making an electric contact device which comprises assembling on a central axially extending insulating support a series of conducting elements of the same shape as each other with intervening insulating washers be-- tween each of the elements, clamping said elements and washers together to form a unit, and removing a portion of material at one side of a central plane perpendicular to the axis to form an inclined plane surface having an edge at an angle to the central axis, removing another portion of material from the same side of said central plane and from the opposite side of said edge to form a plane surface inclined to said firstnamed inclined surface and thereby forming a leg of projecting contact surfaces at an angle to the central axis, and similarly removing two portions of material from the opposite side of said central plane and thereby forming another leg of projecting contact surfaces at an angle to the first-named leg.

3. The method of making an electric contact device which comprises assembling on a central axially extending insulating support a series of conducting elements of the same shape as each other with intervening insulating Washers between each of the elements, clamping said elements and said washers together to form a unit, removing material from a side portion of said unit to form a plane surface, and then removing a portion of material at one side of a central plane perpendicular to the axis to form an inclined plane surface having an edge located in said first-named plane surface at an angle to the central axis, removing another portion of material from the same side of said central plane and from the opposite side of said edge to form a plane surface inclined to said first-named inclined surface and thereby forming a leg of projecting contact surfaces in said first-named plane at an angle to the central axis, and similarly removing two portions of the material from the opposite side of said central plane and thereby forming another leg of projecting contact surfaces at an angle to the first-named leg.

4. The method of making an electric contact device which comprises assembling on a central axially extending insulating support a series of conducting disks of the same shape as each other and each having an outward extension therefrom and with intervening insulating washers between each of the disks, clamping said disks and washers together to form a unit with the said extension of each disk positioned at one side of the unit, removing material from the opposite side of the unit to form a plane surface, and then removing a portion of material at one side of a central plane perpendicular to the axis to form an inclined plane surface having an edge located in said first-named plane surface at an angle to the central axis, removing another portion of material from the same side of said central plane and from the opposite side of said edge to form a plane surface inclined to said first-named inclined surface and thereby forming a leg of projecting contact surfaces in said first-named plane at an angle to the central axis, and similarly re- 2,429,048 7 moving two portions of the material from the opposite side of said central plane and thereby forming another leg of projecting contact surfaces at an le to the first-named leg. Number ARTHUR M. COHEN. 5 1,280,892 1,280,893 REFERENCES CITED 2340579 The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Steenstrup Oct. 8, 1918 Steenstrup Oct. 8, 1918 Cohen Feb. 1, 1944 Rabbezzana Aug. 16, 1932 Schuh Apr. 28, 1942 

